In the industry it is common to use valves to control and to regulate flows of e.g. liquids. Such valves can for instance be used in dairy plants where there is a large need for controlling different liquids such as milk in different processes or cleaning agents for cleaning the valves, pipes in the system and for cleaning tanks.
Such a valve can be used to secure a closed connection between two separate pipe systems, between a tank and a pipe system or the like.
When used in dairy plants or other places where for instance foodstuffs are prepared and/or handled there is a high demand for a hygienic solution. During use of the valves the product e.g. milk will enter into small crevices between gaskets and structural parts such as a valve seat, bushings in the valve bonnet and so on, and deposit there. During a cleaning sequence this product has to be cleaned away and any bacteria left in these critical places has to be removed to obtain a clean and bacteria free environment.
When a valve consists of several stainless steel parts with gaskets and bushings, a satisfying cleaning result can be quite a challenge.
It is common to use stainless steel in such valves and valve parts due to the robustness regarding corrosion, but the different steel parts have to be held at a small distance to avoid seizing as this tends to happen when stainless steel components slide upon each other. By using bushings of e.g. a low friction polymer or rubber this can be avoided, but then there will be a number of services between the different parts, which can be difficult to clean sufficiently.
Additionally, there is a need to use gaskets or sealing lips to secure the needed tightness of the valve. Also the area between such sealing lips and the actual structural part is difficult to clean.
From WO 2009/071217 A1 a solution for obtaining a valve with a valve plug, where the parts are easy to clean, as there are no gaskets or sealing in any grooves or the like in the area of the valve plug and the valve seat.